EGR Valve or not???

[UrbanRedneckKid]

Yup. Loose lower intake bolts. Follow the torque sequence, it can be found in the tech library.

Probably wouldn't hurt to just throw a set of gaskets at it anyways. Don't use anything but Ford gaskets if you want it to last more than a year. Good time to do valve cover gaskets too, since they have to come off.

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[e21pilot]

Loose intake bolts sounds like a possibility.

I remember back in my high school days when I worked on my 2.8L V6 Capri. You had to remove the valve cover gaskets to get to the low intake bolts. I assume this is still the same on 4.0 as it is a similar design?

On the 4.0, is it possible to remove the valve covers without taking any of the throttle body off? If so, are all the intake bolts accessible for the torque sequence?

If that's the case than I can probably do this fairly easily over the weekend if I can find a new decent set of valve cover gaskets.

 

[UrbanRedneckKid]

You can tighten then without removing anything, as long as you don't have a crappy tool selection.
The valve covers only have to come off to remove the lower intake.

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[e21pilot]

Great, that makes it simple. I will do it first thing on Saturday. Maybe I will solve this problem that easily.

Too bad I will have to wait for the next smog test (2 years) to find out if it helped!

 

[UrbanRedneckKid]

I noticed a difference on how much better it ran, not like more power, but smoother.

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[HRTKD]

e21pilot, how did you make out? My '91 failed emissions today - high NOx.

I installed headers last year and used a Magnaflow catalytic converter that was supposed to be an OEM equivalent. The O2 sensor was also replaced at that time. So I thought I would be OK. I haven't noticed any pinging but I don't drive it much.

I rebuilt the transmission earlier this month. The y-pipe and O2 sensor had to come out, so maybe I messed up the O2 sensor? It's certainly possible. Are there any obvious symptoms I should see if that was the case?

The intake manifold was resealed two years ago just before a successful emissions test.

I'm going to swap the OEM catalytic converter back in, run some Seafoam through the vacuum line and also check for leaks on the intake manifold and vacuum lines. I'll run some 91 octane fuel and then retest the emissions with my fingers crossed. If it still fails then I'll look at replacing the O2 sensor.

 

[e21pilot]

I never did find anything like an EGR valve on the 1992 Federal 4.0 V6 that I have. NOx are still on the high side but not too to fail the smog test. My next step will be to swap in cat from a low mileage 94 Explorer. With about 120K less miles than my cat, I think it has a good chance of improving my numbers.

To your issue, I have heard the Magnaflow cats are decent as far as aftermarket but never as good as factory of course -- when it comes to platinum, you really get what you pay for.

That said, I have heard of people having trouble with leaks in the exhaust around the O2 sensor. These are leaks that let fresh air get sucked into the exhaust pipe between the exhaust pulses. If I understand it correctly the extra O2 somehow leads to more NOx after is goes through the cat.

You might be able to test for such leaks with soapy water around the y pipe joints while blowing air into the exhaust pipe -- engine off of course.

Just a thought but it might be worth a try. Keeping these pre-OBDII trucks on the road is a little easier to do than the newer ones that seem to through CELs more often.

Good luck.

 

[HRTKD]

After re-installing the OEM catalytic converter my emissions test still failed. In fact, it was even worse! I'm going to run a tank of GTP and then try to pass one more time. If it fails again I'll trade it in, part it out or donate it. I can't sell to a private party here in the Colorado front range without a successful emissions test.

 

[e21pilot]

Sounds like the problems are upstream of the cat in your case. Why don't you post the CO/HC/NOx numbers you are getting. Perhaps those on the board might has more suggestions.

I have read that high NOx numbers can be caused by high combustion temps. Is the engine running hot? I have two 4.0 V6 motors and both of mine generally run in the left corner (cool end) of the thermostat.

For what it's worth, my old 1983 BMW always had a hard time getting through the CA smog test even when it had low miles. Last year I spent some time replacing rubber bushings and hoses to eliminate any vacuum leaks and then I removed the cat and soaked it in a laundry soap bath for two days. After I put it all back together it passed that test with better numbers than ever. Not sure what I did that made the big difference but a little TLC helped a lot.

Good luck to you.

 

[HRTKD]

My current thought is that the engine is running lean due to the JBA headers. On my other truck I could tune for that. Is that even possible on a '91 Ranger?

 

[canyoncritter]

as been said before, heat cooling system in good shape? sounds stupid but check raditor cap. and high comp heads been milled?, and lean condtion will cause nox.

JBA's shouldnt cause a problem as they are 50 state legal. pllugged up injectors or weak fuel pump will. got a auto zone near by?....rent the fuel pressure test kit. check pressure and volume. if I rember right, should fill up a snapple bottle in 30 sec or less.

and no, no EGR on 91 or 92 fed trucks. but the injectors are batch fire.

 

[HRTKD]

I think the cooling system is doing OK. I flushed the coolant and replaced hoses a year ago. I also bled the cooling system. According to the temp gauge on the dashboard the engine is not running hot - even after I ran it hard. The radiator cap was not replaced at the time so that's something that could be done.

I ran 1/3 pint of Seafoam through the intake vacuum line and I'm currently running a tank of GTP through. Between the two I would hope my injectors are getting cleaned.

What does this mean?

but the injectors are batch fire.

 

[HRTKD]

Does anyone know if the O2 sensor in the OEM y-pipe reads both banks or just one? The JBA header y-pipe only has bungs in either bank, not in the collector.

 

[canyoncritter]

91-92 is a single 02 system, so only need for the one O2 sensor.and off only one bank.

batch fire is when a bank of injectors fire all at once...2.9's and early 4.0L's with fed emission are set up this way. in fords case its passenger side and driver side. Meaning all injectors on drivers side fire at one, per 4 strokes of the motor. cali emissions and 93 or 94 and and newer run Sequential is where a injector fires for each cylinder. reason some OHV 4.0L's have a cam sensor and some dont.

 

[HRTKD]

I have a Walker y-pipe in my garage that would have fit the OEM manifolds. The bung for the O2 sensor in the y-pipe is in the collector. So that made me think the O2 sensor in just one bank was a problem.

I don't know if this is a Fed or Cali Ranger. It started out life in Hawaii and was subsequently shipped to Colorado a few years later.